Do drivers have a better chance of surviving car wrecks if they're drunk?

July 9, 2009

Dear Cecil:

There's an old saw about God protecting drunks and fools. I'm particularly interested in the drunks part. Almost nightly, it seems, we hear on the news that a drunk driver killed one or more people in another car but the drunk survived, sometimes without injury. A family member suggested drunks are saved because they've passed out and are more relaxed, but I'm skeptical. Is it just the crashes where the drunk walks away after killing another that make the news?

— PLT, Indianapolis

Cecil replies:

If somebody's going to walk away from a fatal car crash, you really want it not to be the inebriated loser who caused it. However, while all the facts aren't in, there's reason to think drunk drivers sometimes get a break they don't deserve.

We'll call what you're describing the lucky-drunk hypothesis. Although it's been floating around for a long time, scientists apparently first examined it seriously in a 1982 study of trauma victims treated at a Texas hospital (Ward et al, American Journal of Surgery). Roughly a third of the 1,200 patients had been drinking. Drinkers and nondrinkers had equally severe injuries. The surprise: The death rate among nondrinkers was one in six; the death rate among drinkers, one in nine. Complication: the researchers were looking at all kinds of trauma, not just trauma caused by car wrecks.

Subsequent studies have produced mixed results, but even those undercutting the lucky-drunk hypothesis had their puzzling aspects. Some examples:

A two-year study at a Seattle trauma center found intoxicated men had lower death rates and less severe injuries than sober men for all types of trauma except car accidents. (Women didn't see much difference.) Overall, the drunker the victim, the less severe his injuries and the less likely he was to die.

Examining data on more than a million drivers involved in car crashes in North Carolina, a research team headed by Patricia Waller reported in 1986 that drunk drivers were roughly twice as likely as sober drivers to be seriously injured in a car crash and two to four times more likely to die. Oddly, however, they found drivers with blood alcohol concentrations (BACs) between 0.15 and 0.19 percent (i.e., really drunk — legally drunk is 0.08 percent) suffered less severe injuries than those with other, often smaller amounts of alcohol in their system.

A 1992 study in Vermont focused on 427 trauma victims, 43 percent of whom had been in auto accidents. Drinkers (here meaning those with any amount of alcohol in them) suffered more head injuries on average, had six times the death rate of nondrinkers, and were much more likely to suffer from serious injuries. On the other hand, the legally drunk had fewer really bad injuries than the moderate drinkers. The difference wasn't statistically significant, though.

A 1997 review found such studies of alcohol and injury fell into two groups showing opposite results: (1) Research based on reports from emergency personnel generally found alcohol use meant increased risk of serious injury or death. However, the severity of the trauma often stemmed from side effects of drinking such as speeding or not wearing seat belts, not from drinking itself. (2) In contrast, most studies of hospitalized trauma victims found no relation between drunkenness and injury severity, and a few found alcohol had a protective effect. One possible explanation: The EMTs' injury assessment method exaggerated trauma severity in drunks, particularly those with head injuries, who were then more likely to be hospitalized. So you had a lot of hospitalized drinkers whose problems seemed worse than they were, perhaps skewing the results.

No doubt hoping to settle things once and for all, Patricia Waller led a team that published another study in 2003. Taking numerous variables into account, the group looked at data for almost 1,400 car wreck victims and found that, on the whole, alcohol increased injury — but the effect wasn't linear. As in previous studies, injury severity dipped sharply in accident victims showing a BAC between 0.15 and 0.19 percent, but also for victims with BACs above 0.25 percent, or (theoretically at least) very, very drunk. Waller and company thought they could come up with an explanation for the high-end drop (people in that category may have had an unusually high tolerance for alcohol and thus bucked the more-alcohol = more-injury trend), but the midrange dip was a complete mystery.

Conclusions for now:

1. We sure don't know that alcohol protects drunks by making them more relaxed.

2. It does seem to protect them in a limited sense. In general, alcohol makes injuries worse, and no one's saying being drunk is safer than being sober, but research has repeatedly shown that under some circumstances drunks get hurt less than you'd expect. Waller, perhaps the most persistent of the many researchers looking into the lucky-drunk hypothesis, died of cancer in 2003, so it may be a while before we get an answer more definitive than that.